Delayed action detonator

ABSTRACT

A SAFE DELAYED ACTION DETONATOR HAVING AN IGNITER, A DELAY COMPOSITION AND AT LEAST A PRIMARY EXPLOSIVE WHERE THE IGNITER AND THE DELAY CHARGE ARE MIXTURES OF SILICON WITH EITHER TITANIUM, ZIRCONIUM OR BOTH.

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[54] DELAYED ACTION DETONATOR 7 Claims, 1 Drawing Fig.

ABSTRACT: A safe delayed action detonator having an igniter, a delay composition and at least a primary explosive where the igniter and the delay charge are mixtures of silicon [5 1] int. with either titanium, zirconium or both.

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INVENTORS HELMUT MEN KE HANS FLORIN BY ATTORNEYS.

DELAYED ACTION DETONATOR This invention relates to detonator for explosives. It more particularly refers to a safer delayed action detonator. A delayed action detonator is constructed according to the following principle; it contains an igniting charge, a delay composition, a primary explosive and a secondary explosive. The igniting charge is usually ignited by friction (friction cap) or electric current (bridge igniters, gap igniters, spark igniters). The flame thereby produced starts the burning of the time-delay charge. The latter then initiates a primary explosive which detonates the secondary explosive which is the actual charge that supplies the explosive force. The processes occurring both in the electric fuse head and in the delay composition are chemical reactions. The delay charges often involve a combustion process and such charges are often made of a mixture containing one component that contains oxygen and another component that reacts with oxygen.

These prior art igniting and delay charges, however, have the following disadvantages: I

1. They do not have sufficient thermal stability, that ls, they are often stable only up to temperatures not exceeding 200C. During long storage, however, these temperature stability limits drop substantially, usually to below 100C. Often decompositions of the chemical compounds occur, which greatly modify the properties of the igniting and delay composition, and under certain circumstances render the charges completely useless.

2. The prior art igniting and delay charges are very sensitive to friction and shock. Therefore, danger is involved in manufacturing and handling them.

3. In many delayed-action detonators which contain the igniting and delay charges of the prior art, sensitivity to ignition by electrostatic charge is quite high.

It is an object of this invention to provide a novel igniting charge and delay charge which are not subject to the disadvantages set forth above.

It is another object of this invention to provide a novel igniting and delay charge which is not dependent upon combustion or chemical oxidation.

Other and additional objects of this invention will become apparent from a consideration of this entire specification including the claims and drawing hereof.

In accord with and fulfilling these objects, one aspect of this invention resides in the use of certain alloyable metals and for metalloids for the igniting and delay charges of a detonator.

The utilization of alloying heat is in the prior art. For example, in an electrical squib (a small electrical igniting unit), a powdered metal mixture of palladium and aluminum is used which performs the function of an electrical resistance wire (cf. electrical resistance wire delayed-action detonators) and of an igniting charge.

However, according to this invention the igniting and delay charges are made of a mixture silicon powder with titanium and/or zirconium powder with the silicon being present in proportion of about 5 to 35 weight percent.

The mixtures according to the invention, when sufficiently heated, enter into an alloy, whereupon so much alloying heat is released that the reaction (alloy formation) initiated in the igniting and delay charges formed by the said mixture reliably progresses.

Mixtures of silicon with titanium or zirconium have the advantage over palladium and aluminum mixtures that their eutectic points are higher, namely they are above l,300 C. for the above-stated weight ratios. This presents the advantage that accidental ignition cannot be so easily produced by electrostatic energies or by friction heat produced by shock or friction.

Furthermore, the silicon-titanium system at 11-17 kcal./gram atom, and the silicon-zirconium system at l2l9 kcal./gram atom, have alloying heats at a level that is probably not exceeded by any other systems.

The embodiment of this invention is shown in the accompanying drawing which is a vertical schematic section through adetonat or accordin to this invention.

The initiator mate 1 consists of a silicon-titamum igniting charge. It is embedded in a cylindrical plastic plug 2 in such a manner that at one end only the head of the match assembly protrudes, while at the other ,end the igniting wires 3 emerge. At the igniting pellet end of the plastic plug, a metal cap 4 is closely fitted over the latter; this cap is also filled with the silicon-titanium mixture as an igniting charge 5, and is compressed with low pressure (approx.' 5,000 lb./in.") against the igniter pellet, so that the latter is well embedded in the charge.

The delay charge 6, also consists of a silicon-titanium mixture. This charge is pressed in with increasing pressure up to 16,300 lb./in.". In the lower portion 7 of the metal cap 8 are contained suitable incendiary charges or explosives. A plastic plug 9 crimped with the cap assures a tight closure of the cap.

On account of the high eutectic point of the mixtures of silicon with titanium or zirconium, it is best to use in the igniting pellet bridge wire made of materials which, like tungsten or molybdenum, have a sufficiently high melting point.

However, copper wires can also be used, because when copper is used as the bridge wire, it forms an alloy with the silicon when heated. The alloying heat thereby produced suffices to initiate the intended alloying with the silicon with titanium or zirconium. The grain sizes of the metal powders amount to about 0.5 to 20' microns, and the surface area thereof is about 0.5 to 10 square meters per gram.

We claim:

1. In a detonator containing an igniting charge, a delay charge, and at least one explosive; the improvement which comprises utilizing as said igniting charge and said delay charge an alloyable powder mixture consisting essentially of about 5 to 35 weight percent silicon and at least one member selected from the group consisting of titanium and zirconium.

2. The improved detonator claimed in claim I wherein said powder mixture igniting charge is compressed to a lesser degree than said delay charge.

3. The improved detonator claimed in claim 1 wherein said metal powders have grain sizes of about 0.5 to 20 microns.

4. The improved detonator claimed in claim 3 wherein said metal powders have a surface area of about 0.5 to 10 square meters per gram.

5. The improved detonator claimed in claim 1 having in addition bridge wire igniting wires selected from the group consisting of tungsten and molybdenum.

6. The improved detonator claimed in claim 1 having in addition bridge wire of copper alloyable with said silicon.

7. The improveddetonator claimed in claim 1 wherein said explosive consists of a primary and a secondary explosive. 

